TP53 and neoplasm: Mutations in p53 gene are described in 10% to 15% of tumours without 1p and 19q loss.17 Such tumours arise most commonly in the temporal lobes; histologically they are anaplastic or mixed oligoastrocytomas and express poor chemosensitivity.50,51 Response rate or efficacy of the chemotherapy treatment was observed only in 33% of patients with p53 mutation and intact 1p and 19q chromosomes, as opposed to tumours with intact p53 gene and 1p and 19q or only 1p mutation, where the response rate was 100%.17,50